The endogenous cardiac hormonal system (CHS) moderates blood pressure, the development of left-ventricular hypertrophy (LVH) in response to hypertension, and delays progression of systolic heart failure. The "afferent-limb" of the CHS refers to the ability of the myocardium to release atrial and brain natriuretic peptide (ANP and BNP) in response to pressure overload, and the "efferent- limb" describes the biological action of these hormones in target tissue. Plasma levels of cGMP are tightly correlated with the efferent actions of the cardiac hormones providing a validated method to measure the efferent function of the CHS in humans. We hypothesize that gene-environment interactions involving genes related to critical components of the afferent and efferent cardiac hormonal signaling pathways, and gene-gene interactions between these genotypes and the ACE-gene, contribute to inter-individual variation in susceptibility to hypertensive heart disease. Moreover, differences in the frequencies of these alleles in special populations may explain the increased susceptibility of African-Americans to LVH, development of heart failure, and progression of established heart failure. In order to address these hypotheses, we will identify patients with untreated hypertension and LVH in a random population sample of approx. 3,000 subjects. We will then compare the afferent and efferent function of the CHS in African- American and Caucasian subjects with untreated hypertension and leftventricular hypertrophy, and identify phenotypes characterized by reduced function of either the afferent or efferent function of the CHS. We will sequence these subjects to identify sequence variants in candidate genes critical to the cardiac hormonal signaling pathways (the gene for ANP, BNP, the type A and C cardiac hormone receptors, and corin). We will then study the association of these genotypes with prevalent hypertension, cardiac MRIdetermined LVH, and prevalent hypertensive cardiomyopathy in the two ethnic cohorts. In addition we will analyze the association of these genotypes with prognosis in patients with advanced systolic heart failure.